1. Field of the Invention
The present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery having the possibility of generating a swelling phenomenon after storing for a long time and conducting a charging/discharging cycle at a high temperature may be effectively restrained, and a lithium secondary battery including the same.
2. Description of the Related Art
Recently, interest on an energy storage technique has been gradually increased. According to the enlargement on an application field of the energy storage technique including a cellular phone, a camcorder, a notebook pc, and even electric vehicles, requirements on the high energy densification of a battery used as a power source of electronic devices have been increased. A lithium secondary battery is a kind of a battery satisfying the requirements best, and researches on the lithium secondary battery have been actively conducted nowadays.
Among the secondary batteries presently used, the lithium secondary battery developed at the early in 1900 includes an anode formed by using a carbon material absorbing and desorbing lithium ions, a cathode formed by using an oxide including lithium and a non-aqueous electrolyte solution obtained by dissolving an appropriate amount of a lithium salt into an organic solvent mixture.
As the application of the lithium secondary battery has been expanded, a demand on a lithium secondary battery maintaining a good performance under a severe condition such as a high temperature or a low temperature, and having a safe charging at a high voltage has been gradually increased.
However, the structural stability and capacity of a lithium transition metal oxide or a complex oxide used as the active material of the cathode of the lithium secondary battery may be determined by the absorption and desorption of lithium ions. The capacity may be increased as the charging voltage increases. In this case, the desorption of the transition metal constituting the active material may be accelerated to induce structural instability.
The organic solvent commonly used in the non-aqueous electrolyte solution may include ethylene carbonate, propylene carbonate, dimethoxyethane, gamma butyrolactone, N,N-dimethyl formamide, tetrahydrofurane, acetonitrile, etc. However, when storing these organic solvents at a high temperature for a long time, the electrolyte solution may be oxidized to generate a gas. Then, a swelling phenomenon may be generated to deteriorate the battery. In this case, the thus decomposed and generated gas may deform a pouch type or a can type battery assembly to induce an internal short. In severe cases, the battery may ignite or be exploded. The oxidation of the electrolyte solution may be accelerated by the transition metal eluted under a high voltage condition.
In order to solve the above described defects, addition of various additives into the non-aqueous electrolyte solution has been suggested to prevent the swelling of the battery. Until now, an effective solution has not been suggested.